docs: update kavaref-android

Author: fankes

docs-source/src/en/library/kavaref-android.md

@@ -3,6 +3,8 @@
 ![Maven Central](https://img.shields.io/maven-central/v/com.highcapable.kavaref/kavaref-android?logo=apachemaven&logoColor=orange&style=flat-square)
 <span style="margin-left: 5px"/>
 ![Maven metadata URL](https://img.shields.io/maven-metadata/v?metadataUrl=https%3A%2F%2Fraw.githubusercontent.com%2FHighCapable%2Fmaven-repository%2Frefs%2Fheads%2Fmain%2Frepository%2Freleases%2Fcom%2Fhighcapable%2Fkavaref%2Fkavaref-android%2Fmaven-metadata.xml&logo=apachemaven&logoColor=orange&label=highcapable-maven-releases&style=flat-square)
+<span style="margin-left: 5px"/>
+![Android Min SDK](https://img.shields.io/badge/Min%20SDK-21-orange?logo=android&style=flat-square)
 
 This is the core base module for KavaRef on the Android platform.
 

docs-source/src/zh-cn/library/kavaref-android.md

@@ -3,6 +3,8 @@
 ![Maven Central](https://img.shields.io/maven-central/v/com.highcapable.kavaref/kavaref-android?logo=apachemaven&logoColor=orange&style=flat-square)
 <span style="margin-left: 5px"/>
 ![Maven metadata URL](https://img.shields.io/maven-metadata/v?metadataUrl=https%3A%2F%2Fraw.githubusercontent.com%2FHighCapable%2Fmaven-repository%2Frefs%2Fheads%2Fmain%2Frepository%2Freleases%2Fcom%2Fhighcapable%2Fkavaref%2Fkavaref-android%2Fmaven-metadata.xml&logo=apachemaven&logoColor=orange&label=highcapable-maven-releases&style=flat-square)
+<span style="margin-left: 5px"/>
+![Android Min SDK](https://img.shields.io/badge/Min%20SDK-21-orange?logo=android&style=flat-square)
 
 这是 KavaRef 在 Android 平台的核心底座模块。